Repeater-controlling system for pour-wire telephone-circuits



C. S. DEMAREST.

REPEATER- CONTROLLING SYSTEM FOR FOUR-WIRE TELEPHONE CIRCUITS.

APPLICATION HLED SEPT. 16. 1919.

1,381,545. Patented June. 14, 1 921.

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(7 ATTORNEY C. S. DEMAREST.

REPEATER CONTROLLING SYSTEM FOR FOUR-WIRE TELEPHONE CIRCUITS, APPLICATION FILED SEPT. 16, 1919.

1 $381,545 Patented June 14, 1921.

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. IN V EN TO R.

[I .ffiemazw! A T TO RN E Y UNITED STATES PATENT OFFICE.

CHARLES S. DEMAREST, OF BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COI'IPANY, A CORPORATION OF NEW YORK.

REPEATER-CONTROLLING SYSTEM FOR FOUR-WIRE TELEPHONE-CIRCUITS.

Specification of Letters Patent.

Patented June 14, 1921.

Application filed. September 16, 1919. Serial No. 324,155.

T 0 all whom it may concern:

Be it known that I, CrIARLns S. Dnimnns'r, residing at Brooklyn, in the county of'Kings and State of New York, have invented certain Improvements in Repeater-Controlling Systems for Four-Wire Telephone-Circuits, of which the following is a specification.

This invention relates to repeater controlling systems for four-wire telephone circuits, and more particularly to means to pre vent the connection of the repeater elements with the said four-wire circuit until the tourwire circuit is connected with a telephone line in each direction and certain predetermined keys associated with the cord circuits are in their normal positions.

In the operation of the four-wire telephone circuitshaving repeater elements associated with each of the two-wire sides of the circuit, it is well known that such circuits will tend to sing unless the four-wire circuit is connected by means of a cord circuit with atelephone circuit in each direction with which it is intended to cooperate and all of the keys except the monitoring key of each cord circuit are in their normal positions. Singing of a repeater circuit arises from the unbalanced condition of the circuit which exists prior to the establishment of the through-line connection. As is well known, the repeater elements associated with such four-wire circuits are operated to give'a gain of sufficient magnitude to overcome the loss not only in the four-wire circuit itself, but also the loss introduced by the cord circuits and the telephone line circuits with which repeater circuit is intended to cooperate.

One of the objects of this invention is to repeaters themselves are connected with the four-wire circuit.

In my co-pending application, Serial Number 278,945, filed February 24, 1919, a

means is described for accomplishing this result which involves the use of marginal relays associated with the sleeve contacts of the jacks of the four-wire circuit. This invention diifers from that described in the pending application in the avoidance of the use of marginal relays and in accomplishing the desired result by means of a simplex circuit over the tip and ring sides of the tour-wire circuit and its associated cord circuits.

Other objects of this invention will appear from the following description when read in connection with the attached drawing, Figure l of which shows a typical toll cord circuit and Fig. 2 shows the four-wire circuit with which the cord circuit is adapted to cooperate.

The toll cord circuit shown in Fig. l terminates in plugs P and P plug I, being adapted for insertion in jacks J and J thereby connecting lines L and L with said cord circuit, and plug P being adapted to be inserted in jacks J 3 and J 4 of the fourwire circult shown in Fig. 2, thereby connecting the tour-wire circuit with the said cord circuit. Lines L and L extend from the toll ofiice A to an ordinary central ofiice and they'may be either ringdown or callcircuit trunks. Associated with the cord circuit are keys 1x K K and K ,-key K being adapted to apply ringing current to the lines L and L key K being a splitting key of the well known type; K when operated toward the left being adapted to connect the operators telephone set with the cord circuit for talking purposes, and when operated toward the right to connect the telephone set for monitoring purposes; and key IQ, being adapted to apply ringing current to the circuit with which the plug P may be connected. An impedance coil, 1, is bridged across the tip and ring sides of the cord circuit and the midpoint of the said coil is connected to conductor 2, which, may be grounded either by the operation of keys K 1& K talking side), and K or by the operation. of the relay R, which is connected with the sleeve of plug P Bridged across the circuit are the supervisory relays R and it which respond to signaling current received over the lines with which the said cord circuit may be connected.

, Fig. 2 represents a tour-wire circuit extending between two toll oi'iices designated A and B and terminatin in jacks J and J at ofiice A and jacks 5 and J G at ofiice B. Jacks J and J, are adapted for connection with the toll cord shown in Fig. l by the insertion of the plug P in either of said jacks. Jacks J and J at ofliee B are, in like manner, adapted to be connected to another toll cord similar in every respect to that shown in Fig. 1 by the insertion in the said jacks of a plug similar to plug P The four-wire circuit shown in Fig. 2 consists of two twowire sides, 3 and a, with which are associated repeater elements 5 and 6 respectively. These elements are shown in the figure as being the well known thermionic devices, but it is to be understood that any well known type of telephone repeater might be substitutecl in place thereof.

These two-wire sides are electrically related by means of the triple winding transformers X and Y, with which are associated net works N and N respectively, which are adapted to balance the telephone lines connected with the 'rourqvire circuit at oilices A and B respectively. The function of net works N and N which are connected with the two-wire terminals at ollices A and B re spectively, is to regulate the transmission gain produced by the repeater circuit so that the transmission equivalent over all throughline connections will be substantially the same. Relay 3,, which is bridged across one of the two-wire sides at o'll'ice A, is responsive to ringing current transmitted over the said side from ofiice B to oflice A and cooperates with relay R to produce a signal at oliice A by the lighting of the lamp 8,. A relay R similar to 11,, cooperates with relay R at oifice B to produce a si nal at otl'ice B by the lighting of the lamp b It will be noticed that the repeater elements 5 and (5 are normally disconnected from the sides of the tour-wire circuit. Switching relays R and R, when operated serve to connect the repeater element 5 with the two-wire side 3, and switching relays R and R serve in a similar manner to connect the element 6 with the two-wire side a, and their operation is controlled by the joint operation of relays R and R Relay R which is associated with the repeater elements, is adapted to connect the batteries B and B, with the filaments of the repeater elements 5 and 6 respectively. At oiiice A relavs It 7 and R associated with the-sleeve contacts of jacks J and J. respectively, and, in like manner, at of'lice B relays R and R associated with jacks J and J respectively, are adapted to control the operation of relays R and R which, in turn, serve to control the operation of the switching relays. Relays E and R at oliice A and office B, respectively, referred to hereafter as the guard relays, serve to prevent the operation of the control relays R and R after the cord circuits have been connected with the jacks at oflices A and B and prior to the time of completion of the through-line talkin connection.

This invention will be more fully understood from the following description of its mode of operation. Assuming, for example, that a si nal has been received at ofiice A over line the operator inserts plug P, in jack J of line L and, by moving key K t0 the left, learns from the other operator at the distant end of line L that a circuit connection is desired which necessitates the use of the four-wire circuit extending between toll offices A and B. The operator A thereupon inserts plug P oi her cord circuit in the jack J of the four-wire circuit, and, by operating ringing key K applies ringing current to the tour-wire circuit, thereby causing the operation of relays R and R7 and, in consequence thereof, the lighting of the lamp S The operator at B inserts a plug similar to plug P of the cord circuit shown in Fi 1 and by operating a key similar to key 1x she is enabled to talk withthe operator at oilice A who has maintained key K in its talking position. Upon receiving the proper instructions from the operator at oflice A the operator at. oliice B thereupon inserts the other plug of the cord circuit in a jacket a trunk line which may be assumed to be of a type similar to line L The operator at oilice B then advises the other operator at the distant end of the trunk line with which she has connected her cord circuit to establish the connection with the desired subscribers telephone.

hen the operator at oilice A inserts the plug P in jack J a circuit is established from battery 33, over the sleeve contacts or the said plug and jack and the winding of relay R to ground. thereby causing the operation of the said relay, which grounds conductor 7 by the closing of the upper contact 8 oi'flsaid relay. Practically simultaneous with the establishment of the circuit just outlined, another circuit is established from battery B winding of relay R, and conductor 9 to the midpoint of the impedance coil 10, thence over the tip and ring sides of the two-wire terminal oi the ourwire circuit and the tip and ring contacts of jack J and plug J to the impedance coil 1, and thence over conductor 2 and contact 11 of key K to ground, which causes the operation of relay R and prevents the es tablishment of a circuit from battery ll winding of relay R thence to the midpoint of winding 13, and over the two w i in parallel to the midpoint oi winding ll thence through conductor 12, contact- 15 of relay R and conductor 7, to ground. Aiter the plug P is inserted in either jack L or J the guard relay R will be operated by the'flow of current over asimpler; circuit established by 'theimpedance coils 10 and 1 whenever conductor 2 is grounded, which, may occur whenever keys K K K, (talking side), and K, are operated and as long as plug P remains disconnected from the jack of the trunk line with which it is intended to cooperate. In a similar manner, the guard relay R at oflice B will be operated whenever the similar keys of the cord circuit at office B are operated and until the plug of the cord circuit is connected with the trunk line with which it is intended to cooperate. It will be'seen that the function of the guard relays R1 and R is to delay the operation of relays R and which control the means to connect the repeater elements with the four-wire circuit, until the conditions are right for conversation between subscribers at the opposite ends of the through-line connection.

Let it be assumed that a complete throughline connection has been established between the two subscribers so that further supervision on the part of the operators is unnecessary. \Vhen this occurs all keys of each cord circuit will be restored to their normal positions, thereby removing the ground from the simplex circuit and releasing the guard relays R and R at oflices A and B respectively. As soon as relay R is released the circuit heretofore described extending from battery B, and winding of relay R to ground over contact 8 of relay R will be established, thereby causing the operation of relay R In a similar manner relay R will be operated by current flowing from battery B through winding of relay R and over a circuit to ground through contact 16 of relay R As soon as relays R and R are jointly operated, their contacts 17 and 18 are closed and a circuit is established from ground over the said contacts, thence over conductors 19, 20, 21, and 22, to the switclnng relays R 3-,, R and R respectively, thereby causing the operation of the said relays, which results in the effective connection of the repeater elements 5 and 6 with their respective sides of the four-wire circuit. Furthermore, relay R, is operated by the closing of contacts 17 and 18 which connects batteries B, and B with the filaments of the repeater elements 5 and 6 respectively, so that the elements will begin to function properly.

It will be apparent from the foregoing description that by means of this invention the control of the connection of telephone repeaters with the sides of a four-wire circuit will be automatic and dependent upon conditions within each cord circuit adapted to connect each end of the four-wire circuit with a trunk line circuit. The means for effecting such control consists in a guard relay or equivalent device which, when operated, delays the operation of the switching relays adapted to connect the repeater elements with the four-wire circuit until the cord circuits are in proper condition for conversation between subscribers at the opposite ends of'through-line circuit. The guard relay may be operated by a flow of current due either to the operation of certain keys of the associated cord circuit or to the non-association of the opposite plug of the cord circuit with the jack of the trunk line circuit with which it is intended to cooperate. Furthermore the path of the current that operates the said guard relay is, in part, a simplexed circuit over the tip and ring sides in parallel of the two-wire terminal of the four-wire circuit and of the cord circuit associated there *ith.

Although this invention has been shown as embodied in a certain form, it is apparent that it is capable of embodiment in other and different forms within the scope of the appended claims.

What is claimed is:

1. In a signaling system, the combination of a four-wire transmission circuit comprising two two-wire side circuits electrically related by means of transformers, a repeater element adapted to be connected with each side circuit, switching means to effect such connection and means for controlling said switching means comprising a relay controlled by the flow of current over a circuit simplexed upon the two-wire terminals of the four-wire circuit and the associated cord circuit whereby said switching means may be prevented from connecting said repeater elements with the side circuits of the fourwire circuits.

2. In a signaling system, the combination of a four-wire transmission circuit comprising two two-wire sides electrically related by means of transformers, cord circuits adapted for connection with each end respectively of said four-wire circuit, a repeater element adapted for connection with each of the two two-wire sides of said transmission circuit and normally disconnected therefrom, switching means to connect said repeater elements with said sides and means for controlling said switching means comprising a relay individual to and electrically connected with each side of the four-wire circuit and governed by the connection of its respective cord circuit with the fourwire circuit and by the relative positions of the keys associated with the said cord circuit.

3. In a signaling system, the combination.

end of said four-wire circuit with a telephone trunk circuit, an impedance coil bridged across the sides of said cord circuits andanother impedance coil bridged also across the sides of each of the two-wire terminals of said four-wire circuit whereby simplexed circuits are established for controlling the operation of said switching means.

4:. In a signaling system, the combination of a four-wire transmission circuit having a plurality of repeater elements associated therewith and normally disconnected therefrom, switching means adapted to connect said repeater elements with said four-wire circuit, cord circuits adapted to connect each end of said four-wire circuit with a telephone trunk circuit and means to control the operation of said switching means normally governed by the connection of said cord circuits with each end of the tour-wire circuit and prevented from operating until the opposite end of each of the said cord circuits is connected with its associated trunk circuit.

5. In a signaling system, the combination of a four-wire transmission circuit having a plurality of repeater elements associated therewith and normally disconnected therefrom, a group of switching relays associated with, each side of said four-wire circuit adapted to connect said repeater elements with the respective sides, and a relay individual to each side and controlled by the connection of its respective cord circuit with the four-wire circuit whereby the operation of said switching relays may be controlled.

In testimony whereof, I have signed my name to this specification this 12th day of September, 1919.

CHARLES S. DEMAREST. 

